1. Field of the Invention
This invention relates to a stacked type fuel cell and, more particularly, to a design enabling recovery of the electrolyte in the stacked-cell body of the fuel cell.
2. Description of the Related Art
As is well known, a fuel cell is a kind of generator which has fuel electrodes and oxidant electrodes facing each other, an electrolyte matrix being provided between these electrodes, and the fuel cell is operated while being supplied with a fuel gas and an oxidant gas.
Fuel cells are grouped into the phosphoric acid type, the sulfuric acid type, the alkali type, the molten carbonate type and so on depending upon the kind of electrolyte employed.
The following description is made with respect to a phosphoric acid type of fuel cell by way of example. However, the same can be said with respect to other types of fuel cells.
In a stacked type of fuel cell using a liquid electrolyte during operation, e.g., a phosphoric acid type of fuel cell, there is a problem in that the electrolyte escapes from the cell and drips flow downward on the side of the stacked-cell body if the moisture absorption expansion heightens.
FIG. 1 shows a perspective view of a stacked type of fuel cell, such as the one disclosed in Japanese patent Laid-Open No. 59-108278, which is constituted by single cells and gas separating plates which are stacked alternately. Seal members 21 for retaining the phosphoric acid are disposed between the single cell 20 layers. Receivers 1 for receiving a certain amount of electrolyte are provided on a side surface of a stacked-cell body 1A of the full cell such as to extend outwardly from the gas separating plates 2. The receivers 1 are also used at the time of replenishment of the electrolyte on the basis of a method of directly supplying the electrolyte to the receivers 1 or a method of flowing a large amount of diluted electrolyte over the uppermost stage of the stacked-cell body 1A so that the amounts of electrolyte received by the receivers 1 are absorbed by the respective cells. Concerning the latter, Japanese Patent Laid-Open No. 61-47073 (U.S Pat. No. 4,596,749) discloses details of the procedure of replenishing an electrolyte to a fuel cell having the same cell structure as that shown in FIG. 1.
It is possible, with the receivers 1 shown in FIG. 1, to recover any electrolyte dripping from reaction gas flow paths and the seal members 21. However, it is impossible to recover that part of the electrolyte which is discharged as vapor and mist through the reaction gas flow paths together with the reaction gas.
A method of recovering electrolyte vapor and electrolyte mist is disclosed in Japanese Patent Laid-Open No. 57-12607 (U.S. Pat. No. 4,345,008). In this method, outlet portions of the reaction gas flow paths are filled with a porous material while the number of cooling pipes disposed in the vicinity of these flow paths is increased in order to reduce the temperature of the flow paths, thereby enabling the electrolyte to be caught together with any condensed water generated in the fuel cell. However, since the outlet portions of the reaction gas flow path are filled with a porous material, pressure loss takes place owing to the condensation of the generated water, and the pressure loss changes to a large extent depending upon the degree of condensation of the generated water including the electrolyte, which is a serious problem. For this reason, it is possible that the flow rate will be reduced to almost zero in some of the reaction gas flow paths while suitable low rates are maintained in other flow paths, resulting in serious deterioration of the cell characteristics and in a reduction in the life of the cell. In addition, since the reaction gas flows against the resistance of the porous members, the electrolyte tends to be discharged again in the form of mist from the porous members to the side of the stacked-cell body, and it is not possible to recover the amount of electrolyte thereby discharged.
The thus-constructed conventional stacked-type fuel cell lacks a means to effectively recover any electrolyte flowing out or discharged as vapor and/or mist from respective cells and return them to the cells. Thus, in the conventional arrangement, there is a problem of cross-over due to insufficiency of electrolyte in the cell or of corrosion of the exhaust gas piping due to attachment of the electrolyte thereto.